1. Field of the Invention
The present invention relates to an image forming apparatus.
2. Description of the Related Art
Conventionally, paper fill-out forms such as an application form, questionnaire, or answer sheet are filled out by a person to express his intentions by selecting an answer to a question among the given alternatives and marking a predetermined place on the form using a writing instrument such as a pencil, ballpoint pen, or a fountain pen. If a wrong place is marked with a pencil, the incorrect mark is erased with an eraser and the correct place is remarked. In the case where a ballpoint or a fountain pen is used, an incorrect mark is crossed out, and another place is marked.
In recent years, such paper forms have come to be digitized and used as electronic forms. An electronic form is represented by electronic data that includes entry spaces as a plurality of fields corresponding to the entry columns of a paper fill-out form. When such an electronic form is used, the user uploads the electronic form on his computer system and displays it on a display device, and the necessary information is inputted by operating an input device such as a keyboard or a mouse pointer. The inputted information is obtained by the system as electronic data and can be sent to the organization to which the form is to be submitted, for example through a network.
However, a user who does not have sufficient knowledge of how to operate a personal computer, or is not very good at keyboard input, often finds it difficult to use such electronic forms skillfully. Rather, it is easiest for such user to fill out a conventional paper form using a conventional writing instrument.
More recently, a pen-style input device referred to as a “digital pen” or an “electronic pen” has been introduced as an effective input device for such a user. (In the present specification, the input device will be referred to as a “digital pen” hereinafter.) A digital pen is used in pairs with a “special paper” on which a prescribed dot pattern is formed. In addition to a conventional ink-type pen nib, the digital pen is equipped with a miniature camera for reading a dot pattern on the special paper, as well as a wireless communication unit. When the user writes a character on the special paper with the digital pen, the miniature camera detects the dot pattern on the special paper with the movement of the pen, and inputted data such as the character written by the user is obtained. This data is sent to a terminal device such as a personal computer or a cellular phone in the vicinity of the digital pen by the wireless communication unit. A system which uses this digital pen can be used as an input device in place of a keyboard or a mouse pointer, and it is easy to use for a user who has difficulties with operating a personal computer or a keyboard. Contemporaneously, it can be used for organizations such as a public office or a financial institution to which the form can be submitted, in that the entry of the user can be acquired as inputted electronic data instead of a conventional paper fill-out form, so that the data can be used directly in electronic processing. (For example, refer to U.S. Pat. No. 6,502,756).
A paper printed by an offset printing machine using a form plate on which a dot pattern is originally set up is generally used as the above-mentioned special paper for the digital pen. The dot pattern can also be printed by an electrophotographic image forming apparatus connected to a computer. An electrophotographic image forming apparatus is very useful in that a number of special papers can be printed as needed.
However, it can be difficult for an electrophotographic image forming apparatus to always stably output a dot pattern, due to the environment in which the apparatus is placed or the wear pattern of the photosensitive drum or the developing device. Therefore, depending on the circumstances, the dot pattern can become too light for the digital pen to read, or the dot pattern can become too dark that it becomes overly conspicuous. In the case where the dot pattern is too dark, it also leads to wasteful toner consumption.